package common.gson;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.Collection;

import org.hibernate.collection.internal.PersistentBag;

import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.internal.$Gson$Types;
import com.google.gson.internal.ConstructorConstructor;
import com.google.gson.internal.ObjectConstructor;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;

import models._Model;


/**
 * 自定义CollectionTypeAdapterFactory，使json内的数组为null时，返回空数组而不是null对象
 */
public final class CollectionTypeAdapterFactory_ implements TypeAdapterFactory {
	private final ConstructorConstructor constructorConstructor;

	public CollectionTypeAdapterFactory_(ConstructorConstructor constructorConstructor) {
		this.constructorConstructor = constructorConstructor;
	}

	public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
		Type type = typeToken.getType();

		Class<? super T> rawType = typeToken.getRawType();
		if (!Collection.class.isAssignableFrom(rawType)) {
			return null;
		}

		Type elementType = $Gson$Types.getCollectionElementType(type, rawType);
		TypeAdapter<?> elementTypeAdapter = gson.getAdapter(TypeToken.get(elementType));
		ObjectConstructor<T> constructor = constructorConstructor.get(typeToken);

		@SuppressWarnings({ "unchecked", "rawtypes" }) // create() doesn't define a type parameter
		TypeAdapter<T> result = new Adapter(gson, elementType, elementTypeAdapter, constructor);
		return result;
	}

	private static final class Adapter<E> extends TypeAdapter<Collection<E>> {
		private final TypeAdapter<E> elementTypeAdapter;
		private final ObjectConstructor<? extends Collection<E>> constructor;

		public Adapter(Gson context, Type elementType, TypeAdapter<E> elementTypeAdapter,
				ObjectConstructor<? extends Collection<E>> constructor) {
			this.elementTypeAdapter = new TypeAdapterRuntimeTypeWrapper_<E>(context, elementTypeAdapter, elementType);
			this.constructor = constructor;
		}

		public Collection<E> read(JsonReader in) throws IOException {
			if (in.peek() == JsonToken.NULL) {
				in.nextNull();
				// 这里做了修改，原先是返回null，改为返回空数组
				return constructor.construct();
			}

			Collection<E> collection = constructor.construct();
			in.beginArray();
			while (in.hasNext()) {
				E instance = elementTypeAdapter.read(in);
				collection.add(instance);
			}
			in.endArray();
			return collection;
		}

		public void write(JsonWriter out, Collection<E> collection) throws IOException {
			try
			{
			 
				if ( collection instanceof PersistentBag )
				{
					out.beginArray() ;
					for( E e: collection ) {
						_Model model = (_Model) e ;
						out.value(model.id) ;
					}
					out.endArray() ;
				}
				else
				{
					if (collection == null) {
						out.nullValue();
						return;
					}
	
					
					out.beginArray();
					for (E element : collection) {
						elementTypeAdapter.write(out, element);
					}
					out.endArray();
				}
			}
			catch( Throwable e )
			{
				System.err.println( "out->"+ out );
				System.err.println( "elementTypeAdapter->"+ elementTypeAdapter );
				System.err.println( "write->"+ e.getMessage() );
//				System.err.println(GBuilder.toJson(collection));
			}
		}
	}
}
